The present invention relates to an acoustic element having a plate-like structure.
The method further relates to a method for sound processing, in which at least at least one property of a sound field is measured, and on the basis of the measurement result an attenuation sound is produced by at least one actuator.
In order to determine acoustic variables, both the sound pressure and the particle velocity must be known. These may also be used to determine acoustic impedance, which is the quotient of the sound pressure and the particle velocity. To control acoustic properties by active control methods and equipments, it must be possible to measure and adjust the aforementioned variables.
It is known to employ an electrostatic loudspeaker made of perforated plate for producing sound. The loudspeaker has a plate-like structure, but its drawbacks include a strong resonating tendency of the plate structure. In addition, electric shielding of the structure is problematic.
It is the object of the present invention to provide a simple and efficient acoustic element and method for sound processing.
The acoustic element according to the invention is characterized by comprising at least one porous stator plate which is either electrically conductive or plated on at least one side to be electrically conductive, and at least one moving diaphragm with at least one electrically conductive surface.
The method according to the invention is further characterized in that at least two dipole sensors and at least two dipole actuators, said sensors and actuators consisting of at least one porous stator plate which is either electrically conductive or plated on at least one of its sides to be electrically conductive and of at least one moving diaphragm with at least one electrically conductive surface, constitute a sandwich structure in which the sensor signals are coupled to control the moving of the dipole actuators for adjusting the sound pressure and the particle velocity to match the desired value signals.
The basic idea of the invention is that the acoustic element consists of at least one porous stator plate which is electrically conductive or plated on at least one of its surfaces to be electrically conductive, and of at least one dielectric moving diaphragm with at least one electrically conductive surface. The idea of another embodiment is that the element consists of at least two porous stator plates and a moving dielectric diaphragm between them. The idea of yet another embodiment is that the moving diaphragm is permanently charged as an electret diaphragm. Further, the idea is that the elements according to the invention constitute a sandwich structure so that it has at least two dipole sensors and at least two dipole actuators, the sensor signals being coupled to control the moving of the actuators for adjusting the sound pressure and the particle velocity to match the desired value signals.
The invention provides the advantages that the element has a simple structure, problems resulting from resonating are non-existent, and its electric shielding is easy. Further, the sandwich structure contributes to efficient production, measurement and attenuation of sound.